$J/\psi$ Pair Hadroproduction at Next-to-Leading Order in Nonrelativistic-QCD at CMS

TL;DR

This study calculates the production of $J/\psi$ pairs at NLO in NRQCD, revealing that current theoretical predictions significantly underestimate experimental results from CMS, indicating the need for new mechanisms.

Contribution

It provides a complete NLO NRQCD calculation of $J/\psi$ pair production, highlighting the importance of the ${}^{1}S_0^{[8]}$ channel and the discrepancy with experimental data.

Findings

NLO NRQCD underestimates CMS data by an order of magnitude.

The ${}^{1}S_0^{[8]}$ channel is crucial at NLO.

Existing models cannot fully explain the observed $J/\psi$ pair production.

Abstract

We perform a complete study on the $J/\psi$ pair hadroproduction at next-to-leading order (NLO) in the nonrelativstic-QCD (NRQCD) framework with the pair of $c\bar{c}$ either in ${}^{3}S_1^{[1]}$ or ${}^{1}S_0^{[8]}$ fock state. It is found that the ${}^{1}S_0^{[8]}$ channel contribution at NLO is essential. Our results indicate that for the CMS, the NRQCD predictions can not describe the experimental data at all, and the total cross section predicted by NRQCD is smaller than the experimental data by an order of magnitude. So new mechanisms are needed to understand the CMS data for $J/\psi$ pair production.